A program of study is underway centered on hepatotoxicity of CC14, BrCC13, and related compounds. Major lines of work are (1) to use formation of Diels-Alder adducts as a new route toward quantitative estimation of lipid conjugated dienes. The latter appear when lipids peroxidize. (2) to synthesize the 6-chromanol of hexahydrocoenzyme Q4, and to study efficacy of this compound to modulate the lethal effects of CC14. (3) to continue work in progress on the toxicity of BrCC13 with methods used for study of toxicity of CC14. In particular, capacity of BrCC13 to produce in vivo lipid peroxidation is under investigation. (4) to carry out the in vitro conversion of CC14 to CHC13 in a liver microsome system supplemented with NADPH. This system should provide a means for studying relative toxic effects of lipid peroxidation and carbon-chlorine bond cleavage on the mixed function oxidase system.